Bone is a specialized connective tissue comprising many cell types, extraccllular matrix, and minerals. The bone marrow is comprised of stromal and hematopoietic cells.
The stromal compartment of the bone marrow is in itself comprised of a heterogenous cell population including, inter alia, bone-forming cells, known as osteoblasts, which originate from osteoprogenitor cells. Ostcoblasts differentiate into osteocvtcs which are cells surrounded by a mineralized matrix. Very little is known about the mechanisms directing the differentiation of the osteoprogenitors into osteoblasts but it is clear that there is a fine balance between different cellular stages that control the osteoblastic cell renewal and cell loss.
Identification of specific stromal cell types is necessary both for better understanding of the cellular differentiation process in the bone marrow as well as for treatment of various bone diseases. However, to date, specific markers that may be used for recognition and selection of a certain stromal component are very few.
Several antibodies have been developed that recognize cell surface antigens of stromal cells such as the murine IgM monoclonal antibody (MAb) termed STRO-1 which identifies a cell surface antigen expressed by human stromal cells capable of forming CFU-F colonies in vitro (Simmons P. J. et al., STRO-1, Blood, 78:55-62 (1991), the MAb termed 6-19 which binds a surface antigenic determinant expressed on several kinds of human cells including bone marrow stromal cells (Iyer, J., et al., Exp. Hematol, 18:384-389 (1990) and MAb which binds to a cell surface marker of osteoclasts (Oursler MJO, et al., J. Cell Biol. 100:1592-1600 (1985).
Several MAbs obtained by using osteoblastic cells as an antigen have also been reported (Walsh, S., et al., J. Bone Miner Res.,9:1687-1696 (1994) and MAbs which recognize the bone isoenzyme of alkaline phosphatase expressed on the surface of osteoblasts (Tanaka, C., et al., Cancer Res., 46:4853-4857, 1986) were also reported. To date, antibodies that bind specifically to subpopulations of fibroblastic cells are also not available.
Specific markers associated with osteoblasts and fibroblasts that may be used for identifying and selecting osteoblast and fibroblast subpopulations are greatly desired.
Benayahu D. et al., (Journal of Bone and Mineral Research, Vol. 10, Number 10, 1995, Blackwell Science, Inc.) describe in their publication which is incorporated herein in its entirety by reference MAb's which recognize an antigen expressed by osteoblasts.